When Sanford ran for Congress in 1994, Culbertson refused to support financially his longtime friend's campaign, saying he feared the "pitfalls and dangers" Sanford would face as a congressman away from his family. The pair remained friends, but Culbertson says Sanford was incredulous: "He was relentless that it wouldn't happen to him."

Sanford's resolve didn't last. In an agonizing press conference on June 24, the Republican governor of South Carolina confessed: "I've been unfaithful to my wife." After going incommunicado from his staff and family for five days, and creating "a fiction" regarding his whereabouts, a tearful Sanford admitted he had been in Argentina visiting his mistress. He apologized to Jenny Sanford, his wife of nearly 20 years, and to their four young sons.

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Days later, Sanford, 49, admitted to more encounters with Maria Belen Chapur than he'd originally confessed, including a trip to New York City to end the relationship under the supervision of a "trusted spiritual adviser" who accompanied him. Culbertson declined to comment on whether he was the adviser.

Sanford also admitted he'd "crossed lines" physically with other women, but said he'd only committed adultery with Chapur. Still, Sanford called his mistress his "soul mate" and described their sinful relationship as "a love story." Oran Smith of the Palmetto Family Council in Columbia responded: "He's publicly carrying a torch for another woman. And I don't care if you're a governor or a janitor, you just don't do that."

Early on, Sanford said he wouldn't resign, though calls for his resignation mounted, and questions swirled about whether he'd used taxpayer funds in conjunction with visits to Chapur.

The governor's fall is a blow to an already-struggling GOP that had pegged the fiscally and socially conservative Sanford as a potential presidential candidate for 2012. One week earlier, Sen. John Ensign, R-Nev., another evangelical and social conservative, also publicly confessed to adultery.

Sanford's fall proved what Culbertson said he told the governor for years: "You need accountability." Indeed, a string of sex scandals among public officials (see below) has underscored the urgency for ongoing accountability among high-profile politicians who may lead insulated lives.

During his press conference, Sanford said while in Congress (from 1995-2000) he leaned on a Christian accountability group in Washington, D.C., known as "C Street." Overseen by The Fellowship Foundation, the group offers accountability and spiritual support for high-profile politicians. Members of the group reportedly counseled Ensign before his affair became public, and the senator says he's reconciled to his wife. When Sanford's wife discovered his affair last February, the governor said he returned to friends from C Street for help.

The center of the group's activity is a house on Capitol Hill where a handful of congressmen rent rooms and participate in regular prayer and Bible studies. Those living at the C Street house share little about the group, saying that publicizing private accountability might deter public figures who need help.

In an interview with WORLD before Sanford's fall, Sen. Jim DeMint, R-S.C., called the group one of the "best parts of being up here." Michael Cromartie of the Washington-based Ethics and Public Policy Center described the home as a kind of "Christian frat house," saying, "[The politicians] have nothing to hide, but I do think they fear the media misreading them."

Some congressional staffers worry that their bosses' silence about C Street exposes the lawmakers to skeptical media coverage: The Fellowship Foundation runs the C Street house, and also sponsors the National Prayer Breakfast, but says little else publicly about its work.

Public records list the nonprofit Youth With a Mission (YWAM) D.C. as owner of the $1.8 million house on C Street, a fact that surprised YWAM Virginia Director Chris Zinchuck. He says YWAM hasn't had staff or operations in the capital for at least a decade. Zinchuck says a board member pays dues to keep the YWAM D.C. nonprofit status active in case they begin a new project, but says: "It's not our house."

(The Fellowship Foundation could not be reached to clarify ownership of the house it uses.)

If Sanford leaned on C Street while in Washington, Culbertson says by the time he reached the governor's mansion in South Carolina, any accountability system was gone. "He's had very little," said Culbertson, who has counseled the Sanfords since February and led a Bible study for couples at the governor's mansion earlier this year.

It's not that accountability wasn't offered: Culbertson said at least six high-profile politicians and businessmen met with Sanford at the beginning of his first term as governor to press Sanford to meet regularly with other Christian men: "Mark agreed intellectually, but it never happened."

Culbertson said he approached Sanford several more times, but Sanford shrugged him off. In recent weeks, he said Sanford told him: "I'd give anything if I would have done what I said I was going to do."

Another problem: Sanford wasn't actively involved in a local church. In a February interview, Sanford told WORLD he considered the evangelical Seacoast Church in Mt. Pleasant, S.C., his home church, and attended Trinity Episcopal Church when he was in the capital. But Sanford acknowledged he often traveled on Sundays and missed church services.

Culbertson says Sanford's desire to avoid creating a scene when showing up for church also meant the governor would slip in late and leave early when he did attend services. (President Barack Obama has expressed a similar dilemma in trying to settle on a church home in Washington.)

Chuck Colson, founder of Prison Fellowship and a former Nixon confidant who went to prison for his role in Watergate, says spiritual accountability can be rare in Washington and is "a major problem" in politics: "You don't have accountability groups generally because you don't want to confess your sins to someone you may be running against in the future."

Rob Schenck, an evangelical minister who leads a Bible study for lawmakers on Capitol Hill, says accountability groups shouldn't replace the role of the church. For example, he applauds the work of C Street but has worried the group can become too insular: "All the benefits of the church-to properly and sensitively impose discipline on Christians-was missing."

Greg Surratt, the Mount Pleasant minister who Sanford considers his pastor, says his congregation is "heart-broken" over Sanford's fall, but declined to discuss whether he had known about the governor's infidelity before his press conference. Surratt said he will help the Sanfords if they desire his help.

Ultimately, Sanford chose his own path, learning the lesson Culbertson says they discussed often in Bible study: "You can choose your sins, but you can't choose your consequences."

Sanford faces a litany of consequences. His wife, Jenny, said she's willing to reconcile, but wants to see humility and repentance from Sanford. For now, she said she's focused on her children and her Christian faith, saying she would "seek the wisdom of Solomon, the strength and patience of Job, and the grace of God in helping to heal my family."

Sanford also faces political consequences, including damaging an already-fragile Republican Party. Larry Sabato, a political scientist at the University of Virginia, said infidelity by Sanford, Ensign, and other Republicans taints the whole GOP: "If you take conservative positions on social and moral issues, you have to walk the walk, you can't just talk the talk." -with reporting by Emily Belz and Edward Lee Pitts in Washington